I understand, and I feel the same way too.
Seriously, what was the point of making that promise then, if it wasn't going to get anywhere? Nomura could have spared some Sora and Naminé friendship moments, I'm sure, and it would have been nice Sora thanking her in person, not to Kairi, or for Roxas to take that job. It just takes away the meaning to me.
I know Sora = Roxas, and Kairi = Naminé, but they're still separated beings with different personalities, and Sora made that promise to Naminé herself, not Kairi. She and Sora had their own separated pledge, of friends.
Plus, Sora's memories are forgotten, but not lost. Naminé just re-chained the links and the memory of Castle Oblivion was lost in the shadows, or darkness. It's still there. There could have been a moment in KH2, I'm positive, that some light incident could have taken place and bring those memories back. A good example would be Diz's light explosion with the machine. He even said anything could happen, and it returned Riku back to normal. That would be perfect timing and be explainable.
I just wonder what's the reason for Nomura to make Sora forget Castle Oblivion? I know COM was a side-quest, but it still connects to the game, and to Sora, especifically.
Other than Naminé, there's also Roxas and Sora.
I wish they interacted more, or a scene where Roxas helps Sora battle, at least freakin' talk and make the insecurities and confusions clear. I know the two as individuals talked of each other, but it still didn't...fulfill.
All we had that was eye to eye confrontation is that battle, which Sora didn't even know it was Roxas, and the end, but even that was little, as he was talking along with Naminé. Hell, I'm sure Sora still didn't grasp exactly what was going on. Kairi had spent a small time with Naminé when she rescued her, and the blond probably explained it to her, but Sora, as always, remained in the dark about what was happening around him. Which was why he was like "WTH?" when Naminé disappeared into Kairi, while the girl herself remained calm and reached out for Naminé's hand as if she knew.
There could have been a bonding moment between the Somebody and Nobody, and know where they stand, and it would have helped Roxas accept his fate more, all the while, making Sora aware of the truth.
I don't know. Things like that irk me for a reason.